Our invention relates to a transmitting loop arrangement for a vehicle cab signal control system. More specifically, the invention relates to wire loop arrangements by which cab signal or speed control commands are transmitted to trains moving along a railroad track with safety features to eliminate or prohibit the unsafe condition of a train receiving and responding to a signal command intended for a preceding train.
On occasion in a railroad signaling system, especially in a rapid transit train control arrangement, it is advantageous to transmit the cab signal or speed control commands from the wayside control apparatus to the train carried apparatus through wire loops laid parallel to the rails rather than transmitting such signals through the rails themselves. Such an arrangement is applicable to a rapid transit system where short track sections and close headway are desired. Further, in an electrified railroad or rapid transit installation, the wire loops for cab signals make it easier to provide the propulsion current return circuits. Among the advantages of using a loop transmitting arrangement are negligible noise in the transmitted signals induced from the propulsion current, sneak circuit paths for cab signal energy, e.g., through impedance bonds, are not as likely to occur, train carried apparatus does not have to respond to as wide a range of signal levels, and complications of connections to the rails to supply the cab signal energy are eliminated. However, one problem when using loops in this manner for transmitting the cab signal commands to the train is the possibility of a following train also receiving the signal intended for the leading train. This can occur since the loops are not shunted by the train wheel and axle sets, as are the rails, to limit the transmission of the signals behind the train. This problem creates a possibility of an unsafe condition existing in the train operation with the following train receiving a proceed indication which is incorrect and unsafe. A special arrangement or pattern of transmission loops in the selection of the signals transmitted can provide a solution to this problem.
Accordingly, an object of our invention is an improved arrangement of transmitting loops for cab signal commands which prevent the occurrence of unsafe operating conditions.
Another object of the invention is a transmitting loop arrangement for cab signal or speed control commands which inhibits the operation of a following train into a section occupied by a preceding train.
Still another object of the invention is a loop arrangement for transmitting cab signal operating commands to vehicles moving along a stretch of roadway which cuts off the operation of the vehicle carried apparatus to halt an approaching vehicle prior to its entry into the section occupied by the preceding vehicle.
It is also an object of the invention to provide an arrangement of transmitting cab signal and speed commands, from the wayside to train carried apparatus along a stretch of track, which includes wire loops laid parallel to the rails and positioned in each section to couple with train carried apparatus in a preselected pattern to cut off the operation of the train apparatus when the next advance track section is occupied.
Still another object of the invention is a cab signal arrangement for a stretch of railroad track using wire loops in preselected patterns laid parallel to the rails to carry cab signal commands from the wayside controls and a plurality of receiver coils mounted in preselected positions on the train to couple with these loops to transfer the signals to the train apparatus.
Still another object of the invention is a cab signal and speed control system for a stretch of railroad track using a plurality of wire loops laid in preselected patterns between the rails to carry the commands section by section to the train and a plurality of receiving coils mounted in preselected positions on each train to couple with the track loops in order to pick up wayside signals to govern train movement in accordance with advance traffic conditions and to cut off the train apparatus operation at the exit end of a section when the next advance section is occupied so that the following train does not receive and respond to signals transmitted to the preceding train.
Other objects, features, and advantages of our invention will become apparent from the following specification and the accompanying drawings when considered with the appended claims.